feat: extend AI Issue Processor to trigger on issue comments

[mathislucka]

This PR extends the AI Issue Processor workflow to trigger not only when an issue is labeled with 'deepset-ai', but also when a comment is added to an issue that already has the 'deepset-ai' label.

Changes made:

1. Added issue_comment event with created type to the workflow triggers to listen for new comments
2. Modified the conditional check in the job to handle two scenarios:
   • When an issue is newly labeled with 'deepset-ai'
   • When a comment is added to an issue that already has the 'deepset-ai' label

Implementation details:

The implementation uses GitHub's conditional workflow syntax to check:

• If the event type is 'issues' and the label name is 'deepset-ai' (original behavior)
• OR if the event type is 'issue_comment' and the issue contains a label named 'deepset-ai'

For issue comments, we use contains(github.event.issue.labels.*.name, 'deepset-ai') to check if the 'deepset-ai' label is present in the list of labels attached to the issue being commented on.

Testing considerations:

This change can be tested by:

1. Adding a comment to an issue labeled with 'deepset-ai' and verifying the workflow runs
2. Confirming the original functionality still works when an issue is labeled with 'deepset-ai'

The rest of the workflow remains unchanged, so the same API call to the deepset AI Platform will be executed in both trigger scenarios.

Closes #15